An investigation was made of the composition and thermal stability of ultra-violet, ozone-oxidized, and P2S5/(NH4)2S-treated (100) surfaces. In particular, X-ray photo-electron spectroscopy and Auger electron spectroscopy were used to probe the oxide and interface at room temperature and after annealing at various temperatures. The room temperature data indicated that S was buried between the oxide over-layer and the GaAs substrate. This oxide contained various As and Ga bonding configurations which, after moderate annealing, were transformed into more thermally stable phases, such as As2O3 and Ga2O3. Complete desorption of the oxide occurred after annealing at 600C. Heating the sample to 495C caused some S to diffuse towards the oxide surface, while annealing at higher temperatures led to S diffusion into the GaAs substrate. Even after complete desorption of the O, a small amount of S remained in the GaAs lattice.

M.J.Chester, T.Jach, J.A.Dagata: Journal of Vacuum Science and Technology A, 1993, 11[3], 474-80